Urea based nitrogenous fertilizers are described which have reduced water solubility. The fertilizers are intended to provide environmental benefits and economic advantages over urea. The fertilizers are a product of reaction of urea with polyphosphates whereby the urea is trapped within the polyphosphate crystal cage. The fertilizers contain nitrogen, phosphorus and one or more of calcium, magnesium and iron. The fertilizers optionally contain other nitrogen compounds and optionally other micronutrients. The fertilizers are granular.